5.Nxe5? This is a poor move as Qd4 forks the knight at e5 and the pawn at e4. This gives Black control of the centre and an opportunity to do some further damage...

The knight retreats to f3 or d3 leading to Qxe4! and checks the King any defence means losing the opportunity to castle. Instead White can play 6. Ng4 but 6...Qxe4+ 7 Ne3 still leaves Black ahead in development and with the bishop pair.